1. Field of the Invention
This invention relates to a floor covering and more particularly refers to a new and improved multi-layer floor covering adapted for use in sporting arenas.
2. Description of the Prior Art
Today, various synthetic floor coverings, such as tartan etc., are used for the construction of sports-grounds. There is no doubt that these coverings for sports-grounds have become highly economical and their physical characteristics have often led to improved performances. Moreover, the coverings are relatively free from servicing, resistant to exposure and practically abrasion-proof. Synthetic floor coverings generally produce an elasticity without the effect of shock-absorption because they contain rubber scrap or synthetic granules (see e.g. Swiss Pat. Nos. 503 504, 547 915, 550 014 and 565 575). Therefore, in spite of various publications, the injurious effects to the health of performers due to the synthetic floor coverings could not be eliminated. These injurious effects, so called "synthetic surface syndromes", can cause damage due to overstrain as well as cause an increase in the risk of accident. Prof. Dr. med. L. Prokop of the Austrian Institute for Sports Medicine, Vienna, tates after a detailed research that "the use of synthetic tracks for training and contests will cause an increase of certain pathological effects". The research was made with more than 30 different synthetic floor coverings and, among others, included a study of the parameters relevant for the injurious effects to health. The result shows that an unilateral consideration of the rate of elasticity must lead to a false conclusion, since the elasticity can only be determined together with the rate of shock-absorption.
A decisive factor therefor is the strain on the foot in its function as a shock-absorber. On a non-elastic, hard floor the foot's function of shock-absorption is strained to a maximum, but even on an elastic floor the foot is still highly strained. This is due to the fact that the floor's elasticity catapults the developed forces from the floor back to the foot. At the same time, when treading on a synthetic floor covering, the foot develops natural vibrations of 80 to 100 C.P.S. which are to be absorbed by the foot and its muscles and sinews (see "Die Belastung des Bewegungsapparates auf Kunststoffboden" by Dr. med. B. Segesser of the Felix-Platter Hospital (Orthopedic University Clinic) Basel). In addition to the effect of shock-absorption--and not only because of its elasticity--the slide rate of the surface of a floor covering plays an important part with regard to the strain on the human locomotor system. A strong sliding friction, or a non-slip surface, blocks the free movement of the foot and increases the strain on the locomotor system, leading to sprains or rupture of the meniscus. For years, medical people connected with sports and, particularly, athletes have asked for a superior covering. However, until now an appropriate floor covering had not been produced.
The Laboratory for Biomechanics of the Swiss Technical Upper School (ETH), Zurich (Dr. B. Nigg), did research on various floor coverings with regard to the strain on the human locomotor system. Artificial coverings achieved the highest negative results, slightly higher than asphalt, 81% higher than lawn, and 40% higher than conventional cinder-track.